An aqueous polyurethane resin dispersion is a material now substituting for a conventional solvent type polyurethane as an environment-friendly material since it can provide a coating film having adhesive property, abrasion resistance and rubbery properties, and a volatile organic material can be reduced as compared with the conventional solvent type polyurethane.
A polycarbonate polyol is a useful compound as a starting material for preparing a polyurethane resin which is used for preparing a polyurethane resin having durability to be used for a hard foam, a soft foam, a paint, an adhesive, artificial leather, ink binder etc., by the reaction with an isocyanate compound. It has been described that characteristics of the polyurethane resin using the polycarbonate polyol are revealed by high cohesive force due to the carbonate group, and the material is excellent in water resistance, heat resistance, oil resistance, recovery of elasticity, abrasion resistance and weather resistance (see Non-Patent Literature 1). Also, in a coating film obtained by coating an aqueous polyurethane resin dispersion using a polycarbonate polyol as a starting material, it has been known that the film is excellent in light resistance, heat resistance, hydrolysis resistance and oil resistance (see Patent Literature 1).
The aqueous polyurethane resin dispersion using a polycarbonate polyol shows good characteristics as mentioned above, but its characteristics are not necessarily sufficient as compared with those using an organic solvent type polyurethane. In particular, solvent resistance and water resistance of the coated film are insufficient. It has been carried out to introduce a cross-linking structure into a polyurethane resin or to add a crosslinking material such as an epoxy resin and a polyfunctional isocyanate, etc. to carry out cross-linking at the time of curing for the purpose of improving such characteristics. Of these, an aqueous polyurethane resin dispersion having a blocked isocyanate group is stable at normal temperature, so that it has high utilization value as an one-component cross-linkable dispersion having high storage stability (Patent Literature 2 and Patent Literature 3). An aqueous polyurethane resin dispersion using a polycarbonate polyol as a starting material has been known that it has characteristics of having high adhesiveness to an electrodeposition film (Patent Literature 4).
[Patent Literature 1] JP H10-120757A
[Patent Literature 2] JP 2002-128851A
[Patent Literature 3] JP 2000-104015A
[Patent Literature 4] JP 2005-220255A
[Non-Patent Literature 1] “Latest polyurethane material and applied techniques” published by CMC Publishing Co., Ltd., Chapter 2, p. 43